Adolescents with mental health (MH) disorders (MHD) have higher rates of HIV/STI sexual risk behaviors than those in the general population. In Brazil, youth testing positive for HIV had more MH problems than HIV- negative youth; HIV/STI sexual risk reduction is not regularly implemented within MH care for adolescents. The Brazil Ministry of Health has funded members of our team to conduct a regional needs-assessment to implement evidence-based HIV prevention interventions as a pilot for future country-wide dissemination in settings providing MH care (APQ-01246-10; PI: Guimaraes). Our NIMH-funded RCT in Rio de Janeiro (Rio; R01MH065163; PI: Wainberg) promises to provide such intervention for adults with MHD. A comparable evidence-based HIV/STI prevention intervention for adolescents is not available in Brazil; this application targets this need. We propose to a) adapt a U.S. efficacious family-based HIV prevention intervention for youth with MHD (STYLE; R01MH63008; PI: Brown) within the three types of settings providing most of the care to adolescents with MHD in Brazil; and b) pilot test the intervention to examine the acceptability, feasibility, and implementation parameters of the resulting Brazil intervention (STYLE-B) within these settings, and to determine key research parameters in preparation for an efficacy RCT. Using quantitative and qualitative methods we will explore the contextual influences on sexual risk behavior of Brazilian youth ages 13-18 with MHD to inform intervention adaptation; we will leverage the sample of Itaborai Youth (PI: Bordin), a study addressing MH resources for adolescents in Itaborai, a city that is part of the Rio metropolitan area, where we have identified risk. We will then pilot-test STYLE-B with a sample of male and female youth age 13-18 years (n=144) with MHD who are in MH treatment in four community-based sites. Youth/caregiver dyads will receive a full-day group session, return in two weeks for an adolescent/caregiver dyad session, and participate in a half-day group session three months later. Acceptability and feasibility will be assessed using process measures after each session. We will assess change in sexual risk behavior outcomes from baseline to 3- months post-intervention. We will elucidate factors influencing intervention adoption (e.g., recruitment, referrals; resources; climate, readiness and capacity for intervention) within the three service systems for youth with MHD in Brazil. We will develop digital interactive technology to train intervention facilitators. The Brazilian MH/health delivery system with country-wide dissemination of antiretrovirals and focus on improving MH care and HIV/STI prevention among youth with MHD, and the government's involving members of our team in these initiatives indicate that STYLE-B has likelihood of being implemented nationally. Our proposal sets the stage for STYLE-B efficacy testing within real-world MH community service systems, which are the most common settings of MH service delivery both in high- and low-resource areas in Brazil, the US and worldwide.